Where do the bubbles come from?

The child has discovered tips the bottle of purple water upside down into a plastic syringe that he has placed in the funnel. Because the syringe has such a small opening into the funnel, bubbles slowly rise up in the bottle. Compare that to just tipping a bottle upside down with the water pouring out. By placing the bottle into the funnel, the child can watch the bubbles rise. That also gives me the opportunity to ask where do the bubbles come from? Listen to their answers.